Given that it appears on a completely serious site, I'd assume that it isn't a joke. Perhaps if I were a single Catholic, I might look further. Not being a Catholic single, I researched the image instead. It is a stained glass window: The Consecration of St. Mél, Bishop of Longford, by St. Patrick
, by Harry Clarke.
that St. Mél's day is now "observed as a holiday for single people." In the ad, the prominent face is St. Patrick--St. Mél's face is obscured by the "JOIN NOW!" banner.